U.S. patent number 11,447,650 [Application Number 17/000,759] was granted by the patent office on 2022-09-20 for inkjet recording liquid set, printed matter, and inkjet recording method.
This patent grant is currently assigned to KONICA MINOLTA, INC.. The grantee listed for this patent is Konica Minolta, Inc.. Invention is credited to Haruka Moriyama, Takayuki Toeda.
United States Patent |
11,447,650 |
Toeda , et al. |
September 20, 2022 |
Inkjet recording liquid set, printed matter, and inkjet recording
method
Abstract
Provides is an inkjet recording liquid set including at least an
inkjet ink and a pretreatment liquid, wherein the inkjet ink
contains at least a pigment, an organic solvent, water and a
silicone surfactant; the pretreatment liquid contains at least
water-insoluble resin particles and a pigment coagulant; and the
silicone surfactant has a structure represented by the following
Formula (1), ##STR00001## in Formula (1), R represents a hydrogen
atom or a hydrocarbon group having 1 to 4 carbon atoms; X is an
alkylene group having 2 to 6 carbon atoms and may have a branched
structure; EO represents an ethylene oxide group, PO represents a
propylene oxide group, and an order of EO and PO is random; m and n
represent a number of repeating unit structures, m is an integer of
2 to 50, and n is an integer of 0 to 20.
Inventors: |
Toeda; Takayuki (Tokyo,
JP), Moriyama; Haruka (Musashino, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Konica Minolta, Inc. |
Tokyo |
N/A |
JP |
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|
Assignee: |
KONICA MINOLTA, INC. (Tokyo,
JP)
|
Family
ID: |
1000006569317 |
Appl.
No.: |
17/000,759 |
Filed: |
August 24, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210071026 A1 |
Mar 11, 2021 |
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Foreign Application Priority Data
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Sep 6, 2019 [JP] |
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JP2019-162632 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D
11/54 (20130101); B41M 5/0017 (20130101); C09D
11/38 (20130101); C09D 175/04 (20130101); C09D
11/322 (20130101) |
Current International
Class: |
C09D
11/54 (20140101); C09D 175/04 (20060101); C09D
11/38 (20140101); B41M 5/00 (20060101); C09D
11/322 (20140101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2015-124342 |
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Jul 2015 |
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JP |
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2017-137461 |
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Aug 2017 |
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JP |
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2018-016711 |
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Feb 2018 |
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JP |
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Primary Examiner: Zimmermann; John
Attorney, Agent or Firm: Lucas & Mercanti, LLP
Claims
What is claimed is:
1. An inkjet recording liquid set comprising at least an inkjet ink
and a pretreatment liquid, wherein the inkjet ink contains at least
a pigment, an organic solvent, water and a silicone surfactant; the
pretreatment liquid contains at least water-insoluble resin
particles and a pigment coagulant; and the silicone surfactant has
a structure represented by the following Formula (1), ##STR00004##
in Formula (1), R represents a hydrogen atom or a hydrocarbon group
having 1 to 4 carbon atoms; X is an alkylene group having 2 to 6
carbon atoms and may have a branched structure; EO represents an
ethylene oxide group, PO represents a propylene oxide group, and an
order of EO and PO is random; m and n represent a number of
repeating unit structures, m is an integer of 2 to 50, and n is an
integer of 0 to 20.
2. The inkjet recording liquid set described in claim 1, wherein a
content of the silicone surfactant is in the range of 0.1 to 3.0
mass % with respect to the inkjet ink.
3. The inkjet recording liquid set described in claim 1, further
containing a pigment dispersant.
4. The inkjet recording liquid set described in claim 1, wherein
the pigment coagulant is a polyvalent metal salt or an organic
acid.
5. The inkjet recording liquid set described in claim 1, wherein
the water-insoluble resin particles contain a polyurethane
resin.
6. The inkjet recording liquid set described in claim 1, wherein
the water-insoluble resin particles are composite resin particles
in which a polyolefin resin or a polyacrylic resin is emulsified in
a polyurethane resin.
7. A printed matter comprising: a printing layer containing the
inkjet ink; and a pretreatment layer containing the pretreatment
liquid, wherein the inkjet ink and the pretreatment liquid are
contained in the inkjet recording liquid set described in claim
1.
8. An inkjet recording method containing the step of recording an
image on a recording medium of a low-absorbent substrate or a
non-absorbent substrate by using the inkjet recording liquid set
described in claim 1.
9. The inkjet recording liquid set described in claim 1, wherein
the water-insoluble resin particles are formed from a polyester
resin, a polyolefin resin, a polyurethane resin, or a composite
resin composed of a polyolefin resin and a polyurethane resin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The entire disclosure of Japanese Patent Application No.
2019-162632 filed on Sep. 6, 2019 with Japan Patent Office is
incorporated herein by reference in its entirety.
BACKGROUND
Technological Field
The present invention relates to an inkjet recording liquid set, a
printed matter, and an inkjet recording method. In particular, the
present invention relates to an inkjet recording liquid set
excellent in image quality, substrate adhesiveness and ejection
stability even on a low-absorbent substrate or a non-absorbent
substrate, and excellent in hot water resistance of the image
surface when formed into a coating film. The present invention also
relates to a printed matter and an inkjet recording method.
Description of the Related Art
In printing using an aqueous inkjet ink, after the ink has landed
on a recording medium, it penetrates and is fixed to form dots, and
a large number of these dots are collected to form an image. This
dot formation process is important for forming a clear image. It
has been proposed that by using an ink set composed of a
pretreatment liquid and an image-forming ink, it is possible to
improve the image quality and the fix ability with respect to white
stripes and color unevenness in an image, which are particularly
problematic in the image quality (for example, refer to Patent
Document 1: JP-A 2017-137461). However, with the configuration of
Patent Document 1, although the image quality on a low-absorbent
substrate such as coated paper is satisfactory, the effect of image
quality and fixability on a non-absorbent substrate typified by a
film was insufficient.
Therefore, it has been proposed to improve image quality and
fixability on a non-absorbent substrate by using an ink set
combining a specific binder resin and an organic solvent or an ink
set combining an emulsion and a specific coagulant (refer to, for
example, Patent Document 2: JP-A 2015-124342; and Patent Document
3: JP-A 2018-16711). However, in the configuration having excellent
fixability and image quality, a large amount of resin is added to
the ink, and when a large amount of binder resin is added to the
ink, ejection stability from the inkjet head is impaired and it was
difficult to maintain stable image quality. In particular, when
high-speed printing is assumed, it is necessary to simultaneously
secure image quality on a non-absorbent recording medium,
fixability on a substrate, and ejection stability that maintains
stable image quality. Conventional technology could not meet all of
these.
SUMMARY
The present invention has been made in view of the above problems
and situations. An object of the present invention is to provide an
inkjet recording liquid set excellent in image quality, substrate
adhesiveness and ejection stability even on a low-absorbent
substrate or a non-absorbent substrate, and excellent in hot water
resistance of the image surface when formed into a coating film. An
object of the present invention is also to provide a printed matter
and an inkjet recording method.
The present inventors have found out the following in the process
of examining the cause of the above problems in order to solve the
above problems. By using an inkjet recording liquid set in which a
specific surfactant is contained in an inkjet ink, and
water-insoluble resin particles and a pigment coagulant are
contained in a pretreatment liquid, it was found that the image
quality, substrate fixing property, and ejection stability were
satisfied even on a low-absorbent substrate or a non-absorbent
substrate. Further surprisingly, it was found that the hot water
resistance of the image surface is improved when it was formed into
a coating film, which led to the present invention. That is, the
above-mentioned object concerning the present invention is solved
by the following means.
To achieve at least one of the abovementioned objects, an inkjet
recording liquid set that reflects an aspect of the present
invention is as follows.
An inkjet recording liquid set comprising at least an inkjet ink
and a pretreatment liquid, wherein the inkjet ink contains at least
a pigment, an organic solvent, water and a silicone surfactant; the
pretreatment liquid contains at least water-insoluble resin
particles and a pigment coagulate; and the silicone surfactant has
a structure represented by the following Formula (1),
##STR00002##
In Formula (1), R represents a hydrogen atom or a hydrocarbon group
having 1 to 4 carbon atoms. X is an alkylene group having 2 to 6
carbon atoms and may have a branched structure. EO represents an
ethylene oxide group, PO represents a propylene oxide group, and an
order of EO and PO is random. m and n represent a number of
repeating unit structures, m is an integer of 2 to 50, and n is an
integer of 0 to 20.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages and features provided by one or more embodiments of
the invention will become more fully understood from the detailed
description given hereinbelow and the appended drawings which are
given by way of illustration only, and thus are not intended as a
definition of the limits of the present invention, wherein:
The FIGURE is a schematic diagram illustrating an exemplary
configuration of an image forming apparatus according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Hereinafter, one or more embodiments of the present invention will
be described with reference to the drawings. However, the scope of
the invention is not limited to the disclosed embodiments.
The inkjet recording liquid set of the present invention is an
inkjet recording liquid set containing at least an inkjet ink and a
pretreatment liquid, wherein the inkjet ink contains at least a
pigment, an organic solvent, water and a silicone surfactant; the
treatment liquid contains at least water-insoluble resin particles
and a pigment coagulant; and the silicone surfactant has a
structure represented by Formula (1). This feature is a technical
feature common to or corresponding to each of the following
embodiments.
By the above means of the present invention, it is possible to
provide an inkjet recording liquid set excellent in image quality,
substrate adhesiveness, ejection stability, and the hot water
resistance of the image surface when formed into a coating film
even on a low-absorbent substrate or a non-absorbent substrate. It
is also possible to provide a printed matter, and an inkjet
recording method. The mechanism by which the effects of the present
invention are expressed or the mechanism of action has not been
clarified, but is presumed as follows.
Effect of Silicone Surfactant
A silicone surfactant is a surfactant having a polysiloxane
skeleton, and its characteristics are derived from the structure of
polysiloxane. It is generally known that the length of the main
chain formed of a siloxane unit (--Si--O--) controls the ability to
reduce the surface tension. That is, as the siloxane main chain
becomes shorter, the compatibility in the ink is improved and the
surface tension will be lowered. The silicone surfactant provided
with the polysiloxane structure having the structure represented by
Formula (1) in the present invention has the shortest chain unit
for satisfying both of these. It is possible to effectively impart
the wettability of the ink to the low-absorbent substrate or the
non-absorbent substrate. In addition, when controlling the
compatibility of the silicone surfactant according to the
application, it is possible to organically modify the siloxane unit
(--Si--O--) at the site corresponding to the side chain or
terminal. When used in an aqueous ink, it is necessary to make the
silicone surfactant itself highly polar, and in general, polyether
modification using polyethylene oxide or polypropylene oxide is
used. Since the silicone portion is hydrophobic, the polyether
portion is oriented in water or the organic solvent to be
contained, and the compatibility is improved. Therefore, both
ejection stability and wettability will be imparted.
(Effect of Pigment Dispersant)
When high-speed printing is intended, it is required to
instantaneously perform both functions of wetting and spreading of
ink droplets on the film, which is a non-absorbent substrate, and
temporary fixing (pinning) of dots. The silicone surfactant
according to the present invention ensures wettability, and the
pigment coagulant ensures the pinning function, thereby achieving
compatibility. As for the pigment coagulant, since the diffusion
rate into the ink is improved by using the relatively low-molecular
acid or metal salt of the present invention, pinning performance
suitable for high-speed printing is exhibited, resulting in
obtaining good image quality.
(Water-Insoluble Resin Particles)
Polyester, polyolefin, and polyurethane resins are known to have
excellent fixability on non-absorbent substrates such as PP
(polypropylene) and PET (polyethylene terephthalate). However,
since the resin coating film having excellent fixability to PP
applied by the pretreatment liquid is generally hard to be wet with
the aqueous ink, the image quality is likely to be impaired.
Therefore, when combined with the silicone surfactant according to
the present invention, it may be suitably spread on the resin
coating film, and both image quality and fixability will be
achieved. The silicone chain portion of the above-mentioned
silicone surfactant is well adapted to the resin coating film, and
since the ether chain is relatively short and the molecule is
compact, the molecular motion of the surfactant is improved, and it
spreads instantly on the resin coating film. It was further
surprisingly found that the use of the silicone surfactant
according to the present invention improves the hot water
resistance of the image surface when formed into a coating film.
This is because during the ink drying process, the silicone
surfactant is oriented on the surface and the hydrophobic silicone
chains are regularly arranged on the image surface, so that the
final coating film surface is in a state where the silicone groups
are evenly aligned without gaps. It is estimated that the
compatibility between the ink film and the resin coating film was
improved and the hot water resistance was developed.
As an embodiment of the present invention, it is preferable that
the content of the silicone surfactant is in the range of 0.1 to
3.0 mass % with respect to the inkjet ink from the viewpoint that
storage stability is excellent, and ink wettability is effectively
imparted.
Further, it is preferable that the inkjet ink further contains a
pigment dispersant from the viewpoint that the storage stability is
excellent, and the coagulant acts effectively to improve the image
quality.
In addition, it is preferable that the pigment coagulant is a
polyvalent metal salt or an organic acid from the viewpoint that it
has a low molecular weight, it easily diffuses into the inkjet ink,
and the pigment in the inkjet ink is aggregated at a higher speed.
As a result, when high-speed printing is performed, the pinning
property of the inkjet ink is improved even on a low-absorbent
substrate or a non-absorbent substrate, and a high-definition image
is obtained.
It is preferable that the water-insoluble resin particles contain a
polyurethane resin from the viewpoint that effective substrate
adhesion to a non-absorbent substrate may be obtained. Further, it
is preferable that the water-insoluble resin particles are
composite resin particles obtained by emulsifying the polyolefin
resin or the polyacrylic resin in the polyurethane resin from the
viewpoint of suppressing a decrease in compatibility with the
polyurethane resin and the pigment coagulant, which is different
from the use of the polyolefin resin or polyacrylic resin
alone.
The printed matter of the present invention is provided with a
printing layer containing the inkjet ink contained in the inkjet
recording liquid set, and a pretreatment layer containing the
pretreatment liquid contained in the inkjet recording liquid set.
As a result, it is possible to obtain a printed matter having
excellent image quality, substrate adhesiveness, ejection stability
and hot water resistance, even on a low-absorbent substrate or a
non-absorbent substrate.
The inkjet recording method of the present invention records an
image on a recording medium of a low-absorbent substrate or a
non-absorbent substrate by using the inkjet recording liquid set.
This provides an inkjet recording method excellent in image
quality, substrate adhesiveness, ejection stability, and hot water
resistance even on a low-absorbent substrate or a non-absorbent
substrate.
The present invention and the constitution elements thereof, as
well as configurations and embodiments, will be detailed in the
following. In the present description, when two figures are used to
indicate a range of value before and after "to", these figures are
included in the range as a lowest limit value and an upper limit
value.
[Inkjet Recording Liquid Set]
The inkjet recording liquid set of the present invention is an
inkjet recording liquid set containing at least an inkjet ink and a
pretreatment liquid, wherein the inkjet ink contains at least a
pigment, an organic solvent, water and a silicone surfactant; the
treatment liquid contains at least water-insoluble resin particles
and a pigment coagulant; and the silicone surfactant has a
structure represented by the following Formula (1).
##STR00003##
In Formula (1), R represents a hydrogen atom or a hydrocarbon group
having 1 to 4 carbon atoms. X is an alkylene group having 2 to 6
carbon atoms and may have a branched structure. EO represents an
ethylene oxide group, PO represents a propylene oxide group, and an
order of EO and PO is random. m and n represent a number of
repeating unit structures, m is an integer of 2 to 50, and n is an
integer of 0 to 20.
(1) Inkjet Ink
The inkjet ink according to the present invention is an aqueous
inkjet ink containing at least a pigment, an organic solvent, water
and the silicone surfactant.
(1.1) Silicone Surfactant
The silicone surfactant according to the present invention has a
structure represented by Formula (1). In Formula (1), R is
preferably a hydrogen atom, a methyl group, an ethyl group, a
propyl group or a butyl group, and more preferably a hydrogen atom
or a methyl group. In Formula (1), X is preferably an alkylene
group having 3 carbon atoms (that is, a propylene group), m is
preferably an integer of 5 to 20 and n is preferably an integer of
0 to 6. In Formula (1), [EO]m and [PO]n may be in either order. For
example, X is not only bonded to EO, but X may be bonded to PO.
Further, the order of EO and PO is in any order, and EO may be
bonded to PO, and then EO may be bonded further.
Specific examples of the silicone surfactant having the structure
represented by Formula (1) include S-1 to S-8 below, but the
present invention is not limited thereto.
(S-1): In Formula (1), R=a methyl group, X=an alkylene group having
3 carbon atoms, m=9, n=0
(S-2): In Formula (1), R=a butyl group, X=an alkylene group having
3 carbon atoms, m=25, n=6
(S-3): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=3, n=0
(S-4): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=33, n=0
(S-5): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=22, n=16
(S-6): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=9, n=0.
(S-7): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=12, n=3
(S-8): In Formula (1), R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=1, n=0
It is preferable that the content of the silicone surfactant having
the structure represented by Formula (1) is in the range of 0.1 to
3.0 mass % with respect to the entire ink from the viewpoint that
the storage stability is excellent, and ink wettability is
effectively imparted.
The silicone surfactant according to the present invention may be
synthesized, for example, according to the synthetic examples
described in Examples below.
(1.2) Organic Solvent
The organic solvent according to the present invention preferably
contains an alcohol. More preferably, it contains an alcohol having
1 to 3 hydroxy groups.
Preferable examples of the mono-alcohol having one hydroxy group
include methanol, ethanol, propanol, isopropanol, butanol,
isobutanol, secondary butanol, and tertiary butanol. Examples of
the diol having two hydroxy groups include 1,2-ethanediol (ethylene
glycol), 3-oxapentane-1,5-diol (diethylene glycol), 1,2-propanediol
(propylene glycol), 1,3-propanediol, 2-methyl-1,3-propanediol,
2,2-dimethyl-1,3-propanediol, 1,4-butanediol,
2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, and
1,6-hexanediol. Examples of the triol having three hydroxy groups
include 1,2,3-propanetriol, trimethylolpropane, and
trimethylolethane.
In particular, it is preferable to contain at least one of the
following compounds as the organic solvent in terms of superior
storage stability: 1,2-ethanediol (ethylene glycol),
3-oxapentane-1,5-diol (diethylene glycol), 1,2-propanediol
(propylene glycol), 1,3-propanediol, 2-methyl-1,3-propanediol,
2,2-dimethyl-1,3-propanediol, 1,4-butanediol,
2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, and
1,6-hexanediol.
As the organic solvent according to the present invention, other
organic solvents other than the alcohols having 1 to 3 hydroxy
groups may be further used. As the other organic solvent, a
water-soluble organic solvent is preferable, and for example,
amines, amides, and glycol ethers may be preferably
exemplified.
Preferable examples of the amine include ethanolamine,
diethanolamine, triethanolamine, N-methyldiethanolamine,
N-ethyldiethanolamine, morpholine, N-ethylmorpholine,
ethylenediamine, diethylenediamine, triethylenetetramine,
tetraethylenepentamine, polyethyleneimine,
pentamethyldiethylenetriamine, and tetramethylpropylenediamine.
Preferable examples of the amide include formamide,
N,N-dimethylformamide, and N, N-dimethylacetamide.
Preferable examples of the glycol ether include ethylene glycol
monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol
monoethyl ether, diethylene glycol monobutyl ether, triethylene
glycol monobutyl ether, propylene glycol monopropyl ether,
dipropylene glycol monomethyl ether, and tripropylene glycol
monomethyl ether.
When the inkjet ink contains two or mom kinds of organic solvents,
the mass ratio of the glycols and diols with respect to the mass of
the entire organic solvents is preferably 50% or mom.
Further, the content of the organic solvent according to the
present invention is preferably in the range of 10 to 50 mass %
with respect to the inkjet ink from the viewpoint of excellent
storage stability.
(1.3) Pigment
As the pigment according to the present invention, an anionic
dispersed pigment, for example, an anionic self-dispersible pigment
or a pigment dispersed by an anionic polymeric dispersant may be
used. In particular, a pigment dispersed by an anionic polymeric
dispersant is suitable.
As the pigment, conventionally known pigments may be used without
particular limitation, and, for example, organic pigments such as
insoluble pigments and lake pigments, and inorganic pigments such
as titanium oxide may be preferably used.
The insoluble pigment is not limited. Preferable examples of the
insoluble pigment are azo, azomethine, methine, diphenylmethane,
triphenylmethane, quinacridone, anthraquinone, perylene, indigo,
quinophthalone, isoindolinone, isoindoline, azine, oxazine,
thiazine, Dioxazine, thiazole, phthalocyanine, and
diketopyrrolopyrrole pigments.
Specific organic pigments that may be preferably used include the
following pigments.
Examples of a magenta or red pigment are C.I. Pigment Red 2, C.I.
Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment
Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red
48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment
Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment
Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment
Red 177, C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment
Red 222, and C.I. Pigment Violet 19.
Examples of an orange or yellow pigment are C.I. Pigment Orange 31,
C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow
13, C.I. Pigment yellow 14, C.I. Pigment Yellow 15, C.I. Pigment
Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I.
Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94,
C.I. Pigment Yellow 138, and C.I. Pigment Yellow 155. In
particular, in view of the balance of color tone and light
resistance, C.I. Pigment Yellow 155 is preferred.
Examples of a green or cyan pigment am C.I. Pigment Blue 15, C.I.
Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16,
C.I. Pigment Blue 60, and C.I. Pigment Green 7.
Examples of a black pigment am C.I. Pigment Black 1, C.I. Pigment
Black 6, and C.I. Pigment Black 7.
(1.4) Pigment Dispersant
The inkjet ink of the present invention preferably further contain
a pigment dispersant. The pigment dispersant used to disperse the
pigment is not particularly limited, and it is preferably a polymer
dispersant having an anionic group, and those having a molecular
weight in the range of 5,000 to 200,000 may be suitably used.
Examples of the polymer dispersant am styrene, styrene derivatives,
vinyl naphthalene derivatives, acrylic acid, acrylic acid
derivatives, maleic acid, maleic acid derivatives, itaconic acid,
itaconic acid derivatives, fumaric acid, block copolymers having a
structure derived from two or more monomers selected from fumaric
acid derivatives, random copolymers and salts thereof,
polyoxyalkylenes, and polyoxyalkylene alkyl ethers.
The polymer dispersant preferably has an acryloyl group, and is
preferably neutralized with a neutralizing base and added. The
neutralizing base is not particularly limited, and it is preferably
an organic base such as ammonia, monoethanolamine, diethanolamine,
triethanolamine or morpholine. In particular, when the pigment is
titanium oxide, the titanium oxide is preferably dispersed by a
polymer dispersant having an acryloyl group.
The addition amount of the polymer dispersant is preferably in the
range of 10 to 100 mass %, and more preferably in the range of 10
to 40 mass % with respect to the pigment.
It is particularly preferable that the pigment is in the form of a
so-called capsule pigment, in which the pigment is coated with the
above-mentioned polymeric dispersant. Various known methods may be
used to coat the pigment with the polymer dispersant. For example,
a phase inversion emulsification method, an acid precipitation
method, or a method of dispersing a pigment with a polymerizable
surfactant is performed, then, supplying a monomer thereto, and
coating while polymerizing may be preferably exemplified.
Particularly preferable method is a follows: a water-insoluble
resin is dissolved in an organic solvent such as methyl ethyl
ketone, and the acid group in the resin is partially or completely
neutralized with a base; then, a pigment and ion-exchange water is
added and the mixture is dispersed; thereafter, the organic solvent
is removed and water is added according to necessity.
The average particle diameter of the pigment in the inkjet ink in
the dispersed state is preferably in the range of 50 to 200 m.
Thereby, the dispersion stability of the pigment may be improved,
and the storage stability of the ink may be improved. The particle
size of the pigment may be measured by a commercially available
particle size measuring instrument using a dynamic light scattering
method or an electrophoresis method. The measurement by the dynamic
light scattering method is simple, and the particle diameter range
may be measured accurately.
The pigment may be used after being dispersed with a dispersant
together with other necessary additives depending on the desired
purposes.
As a dispersing machine, a ball mill, a sand mill, a line mill, and
a high pressure homogenizer, which are conventionally known, may be
used. Among them, dispersing the pigment by a sand mill is
preferable because the particle size distribution becomes sharp.
The material of the beads used for sand mill dispersion is not
particularly limited, and it is preferably zirconia or zircon from
the viewpoint of preventing formation of bead fragments and
contamination of ionic components. Furthermore, the bead diameter
is preferably in the range of 0.3 to 3 mm.
The content of the pigment in the inkjet ink is not particularly
limited, and a range of 7 to 18 mass % is preferable for titanium
oxide, and a range of 0.5 to 7 mass % is preferable for an organic
pigment.
(1.5) Water
The water contained in the aqueous inkjet ink of the present
invention is not particularly limited, and may be ion-exchanged
water, distilled water, or pure water.
(1.6) Other Components
In the inkjet ink used in the present invention, various additives
known in the art may be used, according to the purpose of improving
the ejection stability, print head and ink cartridge compatibility,
storage stability, image storability, and other various
performances, as necessary. Examples of the additives are
polysaccharides, viscosity modifiers, resistivity modifiers,
film-forming agents, UV absorbers, antioxidants, anti-fading
agents, fungicides, and anti-rust agents. They are appropriately
selected and used. Specific examples are: oil droplets made of such
as liquid paraffin, dioctyl phthalate, tricresyl phosphate, and
silicone oil; UV absorbers described in JP-A 57-74193, JP-A
57-87988, and JP-A 62-261476; antifading agents described in JP-A
57-74192, JP-A 57-87989, JP-A 60-72785, JP-A 61-146591, JP-A
1-95091 and JP-A 3-13376; fluorescent whitening agents described in
JP-A 5942993, JP-A 59-52689, JP-A 62-280069, JP-A 61-242871, and
JP-A 4-219266.
(1.7) Physical Properties
The viscosity of the inkjet ink used in the present invention
having the above constitution is preferably in the range of 1 to 40
mPas at 25.degree. C., and more preferably in the range of 2 to 10
mPas.
(1.8]) Method for Producing Inkjet Ink
The method for producing an inkjet ink according to the present
invention preferably comprises a step of mixing at least a pigment,
an organic solvent, water and a silicone surfactant.
In the mixing step, at least the pigment, the organic solvent,
water, and the silicone surfactant having the structure represented
by Formula (1), and each optional component are mixed at room
temperature or, if necessary, under heating. Then, it is preferable
to filter the obtained mixed liquid with a predetermined filter. At
this time, a dispersion containing the pigment and the pigment
dispersant may be prepared in advance, and the remaining components
may be added and mixed therein.
(2) Pretreatment Liquid
The pretreatment liquid according to the present invention contains
at least water-insoluble resin particles and a pigment coagulant.
The "pretreatment liquid (pretreatment liquid for inkjet
recording)" in the present invention has a function of accelerating
the image formation of ink or improving the image quality when
recording an image on a substrate by an inkjet printing method. It
is one type of ink that is previously applied to the substrate.
Specifically, the pretreatment liquid is a liquid for fixing the
ink at the position where the pretreatment liquid is applied to the
recording medium so that the color ink forming the image does not
spread on the recording medium.
(2.1) Pigment Coagulant
As the pigment coagulant, a polyvalent metal salt, an organic acid
or a cationic polymer may be used, and a polyvalent metal salt or
an organic acid is preferably used. Here, the "pigment coagulant"
refers to a compound that aggregates the pigment contained in the
ink.
(2.1.1) Polyvalent Metal Salt
Examples of the polyvalent metal salt include water-soluble salts
such as calcium salt, magnesium salt, aluminum salt, and zinc salt.
The polyvalent metal salt is capable of aggregating the anionic
component (e.g., anionic resin emulsion) in the aqueous inkjet ink
by salting out.
Further, the content of the polyvalent metal salt is preferably 0.5
to 8.0 mass % with respect to the total mass of the pretreatment
liquid. By setting the content of the polyvalent metal salt within
the above range, bleeding during high-speed printing will be
suppressed.
(2.1.2) Organic Acid
Examples of the organic acid include formic acid, acetic acid,
propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic
acid, citric acid, malonic acid, succinic acid, maleic acid,
benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic
acid and derivatives thereof, methacrylic acid and derivatives
thereof, and compounds having a carboxy group including acrylamide
and derivatives thereof, sulfonic acid derivatives, phosphoric acid
and derivatives thereof.
The organic acid will aggregate the pigment contained in the inkjet
ink. Further, the organic acid will aggregate anionic components
(e.g., anionic resin emulsion) in the aqueous inkjet ink due to pH
change.
The content of the organic acid is preferably an amount that may
adjust the pH of the pretreatment liquid to be less than the first
dissociation constant of the organic acid (for example, 3.5 or
less). The content of the organic acid is preferably 0.5 to 8.0
mass % with respect to the total mass of the pretreatment liquid.
By setting the content of the organic acid within the above range,
bleeding during high-speed printing may be effectively
suppressed.
Since the polyvalent metal salt and the organic acid have a low
molecular weight, they easily diffuse into the aqueous inkjet ink,
so that the pigment in the aqueous inkjet ink will be aggregated at
a higher speed. Accordingly, the inkjet ink of the present
invention will improve the pinning property of the inkjet ink even
on a low-absorbent substrate or a non-absorbent substrate when
high-speed printing is performed, so that a high-definition image
may be obtained.
(2.1.3) Cationic Polymer
Examples of the cationic polymer include diallyldimethylammonium
chloride polymers, polyallylamine polymers, polyvinylamines
polymers, and polyethyleneimine polymers. The cationic polymer will
aggregate anionic components (such as an anionic resin emulsion) in
the inkjet ink.
Further, the content of the cationic polymer is preferably 0.5 to
8.0 mass % with respect to the total mass of the pretreatment
liquid. By setting the content of the cationic polymer within the
above range, bleeding during high-speed printing will be
suppressed.
Since the cationic polymer has a large number of cation sites in
the polymer chain as repeating units, the pigment in the aqueous
inkjet ink will be aggregated at a higher speed. Accordingly, the
inkjet ink of the present invention will improve the pinning
property of the inkjet ink even on a low-absorbent substrate or a
non-absorbent substrate when high-speed printing is performed, so
that a high-definition image may be obtained.
The content of the pigment coagulant may be measured by a known
method. For example, when the pigment coagulant is a polyvalent
metal salt, it may be measured by ICP emission spectrometry, and
when the pigment coagulant is an organic acid, it may be measured
by high performance liquid chromatography (HPLC). When the
coagulant is a cationic polymer, it may be measured by gel
permeation chromatography (GPC).
(2.2) Water-Insoluble Resin Particles
The pretreatment liquid according to the present invention contains
water-insoluble resin particles. It is preferable that the
pretreatment liquid contains a polyurethane resin as the
water-insoluble resin particles. Further, the water-insoluble resin
particles are more preferably composite resin particles obtained by
emulsifying a polyolefin resin or a polyacrylic resin in a
polyurethane resin. The water-insoluble resin particles used in the
present invention are preferably resins that will accept an inkjet
ink and have solubility or affinity for the ink.
Here, "water-insoluble resin particles" means that when the resin
is dried at 105.degree. C. for 2 hours and then dissolved in 100 g
of water at 25.degree. C., the dissolved amount is 10 g or less,
preferably 5 g or less, and more preferably 1 g or less. However,
when the resin has a salt-forming group, the amount of dissolution
is a dissolution value when the salt-forming group of the resin is
100% neutralized with acetic acid or sodium hydroxide, depending on
the type.
(2.2.1) Polyurethane Resin
As the polyurethane resin contained in the pretreatment liquid, one
having a hydrophilic group may be used. Examples of the hydrophilic
group include a carboxy group (--COOH) and a salt thereof, and a
sulfonic acid group (--SO.sub.3H) and a salt thereof. Examples of
the salt include alkali metal salts such as sodium salt and
potassium salt, and amine salts. Among these hydrophilic groups, a
carboxy group or a salt thereof is preferable.
The polyurethane resin is preferably an aqueous dispersion in which
a self-emulsifying polyurethane having a water-soluble functional
group is dispersed in the molecule, or an aqueous dispersion of
forced emulsification type polyurethane prepared by emulsifying
with a strong mechanical shear force using a surfactant. The
polyurethane resin in the aqueous dispersion is obtained by the
reaction of a polyol with an organic polyisocyanate and a
hydrophilic group-containing compound.
Examples of the polyol which may be used for preparation of the
polyurethane resin aqueous dispersion include polyester polyol,
polyether polyol, polycarbonate polyol, and polyolefin type
polyol.
Examples of the polyester polyol include condensation products made
of low molecular weight polyols and polycarboxylic acids. Examples
of the low molecular weight polyol are ethylene glycol, diethylene
glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene
glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol,
3-methylpentanediol, hexamethylene glycol, 1,8-octanediol,
2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A,
trimethylolpropane, and cyclohexane dimethanol. Examples of the
polycarboxylic acid are succinic acid, glutaric acid, adipic acid,
sebacic acid, phthalic acid, isophthalic acid, terephthalic acid,
trimellitic acid, tetrahydrofuranic acid, endomethine
tetralydrofuranic acid, and hexahydrophthalic acid.
Examples of the polyether polyol include polyethylene glycol,
polypropylene glycol, polyethylene polytetramethylene glycol,
polypropylene polytetremethylene glycol, and polytetramethylene
glycol.
Examples of the polycarbonate polyol may be obtained, for example,
by the reaction of a carbonic acid derivative such as diphenyl
carbonate, dimethyl carbonate or phosgene with a diol. Examples of
the diol include ethylene glycol, diethylene glycol, triethylene
glycol, 1,2-propylene glycol, 1,3-propylene glycol, neopentyl
glycol, 1,3-butanediol, 1,4-butanediol, 3-methylpentanediol,
hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol,
bisphenol A, hydrogenated bisphenol A, trimethylolpropane, and
cyclohexane dimethanol.
Examples of the organic polyisocyanate compound that may be used
for preparation of the polyurethane resin aqueous dispersion
include: aromatic isocyanates such as tolylene diisocyanate (TDI),
diphenylmethane diisocyanate (MDI), polymeric (MDI), xylylene
diisocyanate (XDI), and tetramethyl xylylene diisocyanate (TMXDI);
aliphatic isocyanate such as hexamethylene diisocyanate (HMDI);
alicyclic isocyanates such as isophorone diisocyanate (IPDI), and
4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI, H12 MDI).
These may be used alone or in combination of two or more kinds.
Examples of the hydrophilic group-containing compound that may be
used for preparation of the polyurethane resin aqueous dispersion
include: compounds containing a carboxy group such as
2,2-dimethylol propionic acid, 2,2-dimethylol butanoic acid,
2,2-dimethylol butyric acid, 2,2-dimethylol valeric acid, and
glycine, and their derivatives of sodium salts, potassium salts,
and amine salts; compounds containing a sulfonic acid group such as
taurine (i. e., aminoethyl sulfonic acid), and ethoxypolyethylene
glycol sulfonic acid, and their derivatives of sodium salts,
potassium salts, and amine salts.
The polyurethane resin may be obtained by a known method. It may be
obtained as follows. At first, a urethane prepolymer is obtained by
mixing a polyol, an organic polyisocyanate and a hydrophilic
group-containing compound and reacting them at 30 to 130.degree. C.
for 30 minutes to 50 hours.
The obtained urethane prepolymer is extended and polymerized by a
chain extender to obtain a polyurethane resin having a hydrophilic
group. As a chain extender, water and/or an amine compound is
preferably used. By using water or an amine as a chain extender,
the isocyanate-terminated prepolymer may be efficiently elongated
by reacting with a free isocyanate in a short time.
Examples of the amine as a chain extender include aliphatic
polyamines such as ethylenediamine and triethylenediamine; aromatic
polyamines such as meta-xylene diamine and toluylene diamine;
hydrazine; and polyhydrazino compound such as adipic acid
dihydrazide. The amine may contain, together with the
above-mentioned polyamine, a monovalent amine such as dibutylamine
or methyl ethyl ketoxime as a reaction terminator to such an extent
that polymerization is not significantly inhibited.
In the synthesis of the urethane prepolymer, a solvent which is
inert to isocyanate and which dissolves the urethane prepolymer may
be used. Examples of the solvent include dioxane, methyl ethyl
ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone,
toluene, and propylene glycol monomethyl ether acetate. It is
preferable that these hydrophilic organic solvents used in the
reaction step are finally removed.
In addition, in the synthesis of the urethane prepolymer, a
catalyst may be added to accelerate the reaction. Examples thereof
are amine catalysts (e.g., triethylamine, N-ethylmorpholine, and
triethyldiamine), tin-based catalysts (e.g., dibutyltin dilaurate
and dioctyltin dilaurate), and titanium-based catalysts (e.g.,
tetrabutyl titanate).
The number average molecular weight of the polyurethane resin is
preferably as large as possible by introducing a branched structure
or an internal cross-linking structure. The number average
molecular weight is preferably in the range of 50,000 to
10,000,000. When the molecular weight is in the above range, the
polyurethane resin is insoluble in the solvent, a coating film
having excellent weather resistance and water resistance may be
obtained. The number average molecular weight (Mn) is a value
measured by gel permeation chromatography (GPC). For example, by
using "RID-6A" manufactured by Shimadzu Corporation (column: Tosoh
Corporation "TSK-GEL", solvent: tetrahydrofuran (THF) and column
temperature: 40.degree. C.), it may be determined from a
calibration curve prepared with polystyrene standard samples.
The urethane resin may be a commercially available product.
Examples thereof include: "WBR-0160U" (made by Taisei Fine Chemical
Co., Ltd.), "SUPERFLEX 620", "SUPERFLEX 650", "SUPERFLEX 500M" and
"SUPERFLEX E-2000" (made by Dai-ichi Kogyo Seiyaku Co., Ltd.,
"SUPERFLEX" is a registered trademark of the same company) and
"PERMARIN UC-20" (made by Sanyo Chemical Industries, Ltd.,
"PERMARIN" is a registered trademark made of the same company), and
"PARASURF UP-22" (made by Ohara Palladium Chemical Co., Ltd.).
(2.2.2) Polyolefin Resin
Examples of the polyolefin resin contained in the pretreatment
liquid include polyethylene, polypropylene, ethylene-propylene
copolymer, random copolymers or block copolymers of ethylene and/or
propylene with other comonomers (comonomers having 2 or more carbon
atoms such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene,
1-nonene, and .alpha.-olefin comonomers having 2 to 6 carbon atoms)
(e.g., ethylene-propylene-butene copolymers). Moreover, the
substances obtained by co-polymerization of two or more types of
these other comonomers may be used. In addition, two or more of
these polymers may be used by mixing.
The polyolefin resin may be a modified polyolefin such as a
polyolefin modified with an unsaturated carboxylic acid and/or an
acid anhydride. As the modified polyolefin, a polyolefin modified
with an unsaturated carboxylic acid and/or an acid anhydride and/or
a compound having one or more double bonds per molecule is
preferably used.
Examples of an unsaturated carboxylic acid and an acid anhydride
include .alpha.,.beta.-unsaturated carboxylic acids and their
anhydrides. Specific examples thereof are: maleic acid, maleic
anhydride, fumaric acid, citraconic acid, citraconic anhydride,
mesaconic acid, itaconic acid, itaconic anhydride, aconitic acid,
and aconitic anhydride. These may be used alone or in combination
of two or more kinds.
As the compound having one or more double bonds per one molecule, a
(meth)acrylic acid ester monomer may be cited. Examples of the
(meth)acrylic acid ester monomer include methyl (meth)acrylate,
ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
4-hydroxybutyl (meth)acrylate, cyclohexyl (meth)acrylate,
tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl
(meth)acrylate, 2-hydroxybutyl (meth)acrylate, benzyl
(meth)acrylate, glycidyl (meth)acrylate, (meth)acrylic acid,
(di)ethylene glycol di(meth)acrylate, di (meth) acrylic acid
1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, glycerol di(meth)acrylate,
2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl
(meth)acrylate, and acrylamide. Here, (meth)acrylic acid indicates
acrylic acid and methacrylic acid.
In addition to the above-described compounds having a double bond,
stymne, .alpha.-methylstymne, paramethylstymne, chloromethylstymne,
divinylbenzene, vinyl acetate, and vinyl ester of versatic acid may
be used.
Modification of the polyolefin is carried out by dissolving the
polyolefin once in an organic solvent such as toluene or xylene,
and in the presence of a radical generator, by reacting
.alpha.,.beta.-unsaturated carboxylic acid and/or its acid
anhydride and/or a compound having one or mom double bonds per
molecule. Alternatively, in an autoclave which may be reacted in a
molten state capable of raising the temperature to the softening
temperature or melting point of the polyolefin or higher, or in a
uniaxial or biaxial multiaxial extruder, in the presence or absence
of a radical generator, modification may be carried out by reacting
.alpha.,.beta.-unsaturated carboxylic acid and/or its acid
anhydride and/or a compound having one or more double bonds per
molecule.
Examples of the radical generator used in the reaction for
obtaining the modified polyolefin include: peroxides such as
di-tert-butyl perphthalate, tert-butyl hydroperoxide, dicumyl
peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl
peroxyethyl hexanoate, tert-butyl peroxypivalate, methyl ethyl
ketone peroxide, and di-tert-butyl peroxide; and azonitrile
compounds such as azobisisobutyronitrile and
azobisisopropionitrile. When graft copolymerization is carried out
using these peroxides, the amount of peroxide is preferably in the
range of 0.1 to 50 parts by mass, particularly preferably in the
range of 0.5 to 30 parts by mass with respect to 100 parts by mass
of the polyolefin.
The polyolefin resin may be manufactured by a publicly known
method, and there is no limitation in particular about each
manufacturing method or modification degree.
The polyolefin resin used in the present invention preferably has a
weight average molecular weight (Mw) in the range of 20,000 to
100,000. When the weight average molecular weight (Mw) of the
polyolefin resin is 20,000 or more, the cohesive force of the image
formed on the low-absorbent substrate or non-absorbent substrate
(coating film) becomes strong, the adhesiveness of the coating film
will be improved. When the weight average molecular weight (Mw) is
100,000 or less, the solubility with respect to the organic solvent
is good, and particle size reduction of the emulsified dispersion
is accelerated. The weight average molecular weight (Mw) is a value
measured by gel permeation chromatography (GPC). For example, by
using "RID-6A" manufactured by Shimadzu Corporation (column Tosoh
Corporation "TSK-GEL", solvent: tetrahydrofuran (THF) and column
temperature: 40.degree. C.), it may be determined from a
calibration curve prepared with polystyrene standard samples.
A commercially available product may be used as the polyolefin
resin. Examples of the commercially available product include
"ARROWBASE SB-1200" (made by Unitika Ltd., "ARROWBASE" is a
registered trademark of the same company), "AUROREN 150A" and
"AUROREN AE-301" (made by Nippon Paper Industries Co., Ltd.,
"AUROREN" is a registered trademark of the same company),
"SUPERCHLON E415" (made by Nippon Paper Industries Co., Ltd.,
"SUPERCHLON" is a registered trademark of the same company), and
"HARDLEN Na-1001" (made by Toyo Kasei Co., Ltd., "HARDLEN" is a
registered trademark of the same company).
(2.2.3) Polyacrylic Resin
In the present invention, a polyacrylic resin may be used as the
water-insoluble resin particles. The polyacrylic resin may be
obtained by using a copolymer with an acrylic acid ester component,
a methacrylic acid ester component, or a styrene component.
Examples of the acrylic acid ester component and the methacrylic
acid ester component include methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
4-hydroxybutyl (meth)acrylate, cyclohexyl (meth)acrylate,
tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl
(meth)acrylate, 2-hydroxybutyl (meth)acrylate, benzyl
(meth)acrylate, glycidyl (meth)acrylate, (meth)acrylic acid,
(di)ethylene glycol di(meth)acrylate, 1,4-butanediol
di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, glycerol di(meth)acrylate,
2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl
(meth)acrylate, and acrylamide.
Examples of the styrene component include styrene, 4-methylstymne,
4-hydroxystymne, 4-acetoxystymne, 4-acetylstymne and
styrmnesulfonic acid. These components may be used alone or in
combination of two or mom kinds.
The number average molecular weight (Mn) of the polyacrylic resin
is preferably 1,000 to 50,000, mom preferably 2,000 to 20,000. When
the number average molecular weight (Mn) of the polyacrylic resin
is 1,000 or more, the cohesive force of the coating film becomes
strong and the adhesiveness is improved, and when it is 50,000 or
less, the solubility in an organic solvent is good, and particle
size reduction of the emulsion dispersion is accelerated. The
number average molecular weight (Mn) is a value measured by gel
permeation chromatography (GPC). For example, by using "RID-6A"
manufactured by Shimadzu Corporation (column: Tosoh Corporation
"TSK-GEL", solvent: tetrahydrofuran (THF) and column temperature:
40.degree. C.), it may be determined from a calibration curve
prepared with polystyrene standard samples.
A commercially available product may be used as the polyacrylic
resin. Examples of the commercially product of the polyacrylic
resin include acrylic emulsions such as DELPET 60N, 80N (made by
Asahi Kasei Corporation, "DELPET" is a registered trademark of the
same company), DIANAL BR52, BR80, BR83, BR85, BR88 (made by
Mitsubishi Chemical Corporation, "DIANAL" is a registered trademark
of the same company), KT75 (made by Denka Co., Ltd.), and VINYBLAN
2680, 2682, 2688, 2685 (made by Nissin Chemical Industry Co., Ltd.,
"VINIBLAN" is a registered trademark of the same company).
(2.2.4) Polyester Resin
In the present invention, a polyester resin may be used as a
water-insoluble resin particle. The polyester resin is obtained by
using a polyhydric alcohol component and a polycarboxylic acid
component such as polycarboxylic acid, polycarboxylic acid
anhydride, and polycarboxylic acid ester.
Examples of the polyhydric alcohol component include: divalent
alcohols (diols) such as alkylene glycols having 2 to 36 carbon
atoms (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,
14-butlene glycol, and 1,6-hexanediol), alkylene ether glycols
having 4 to 36 carbon atoms (diethylene glycol, triethylene glycol,
dipropylene glycol, polyethylene glycol, polypropylene glycol, and
polybutylene glycol), alicyclic diols having 6 to 36 carbon atoms
(1,4-cyclohexanedimethanol and hydrogenated bisphenol A), adducts
of the alicyclic diols with alkylene oxide having 2 to 4 carbon
atoms (ethylene oxide (abbreviated as EO), propylene oxide (PO),
and butylene oxide (BO)) (adduct mole number 1 to 30), adducts of
bisphenols (bisphenol A, bisphenol F, and bisphenol S) with
alkylene oxide having 2 to 4 carbon atoms (EO, PO, and BO) (adduct
mole number 2 to 30). These may be used alone or in combination of
two or more kinds.
Examples of the polycarboxylic acid component include: divalent
carboxylic acid (dicarboxylic acid) such as alkanedicarboxylic
acids having 4 to 36 carbon atoms (succinic acid, apidic acid, and
sebacic acid), alkenyl succinic acids (e.g., dodecenyl succinic
acid), alicyclic dicarboxylic acids having 4 to 36 carbon atoms
(dimer acid (e.g., dimerized linoleic acid), alkene dicarboxylic
acids having 4 to 36 carbon atoms (maleic acid, fumaric acid,
citraconic acid, and mesaconic acid), and aromatic dicarboxylic
acids having 8 to 36 carbon atoms (phthalic acid, isophthalic acid,
terephthalic acid or derivatives thereof, and naphthalene
dicarboxylic acid). These may be used alone or in combination of
two or more kinds.
The number average molecular weight (Mn) of the polyester resin is
preferably in the range of 1,000 to 50,000, and more preferably in
the range of 2,000 to 20,000. When the number average molecular
weight (Mn) of the polyester resin is 1,000 or more, the cohesive
force of the coating film becomes strong and the adhesiveness is
improved, and when it is 50,000 or less, the solubility in an
organic solvent is good and particle size reduction of the emulsion
dispersion is accelerated. The number average molecular weight (Mn)
is a value measured by gel permeation chromatography (GPC). For
example, by using "RID-6A" manufactured by Shimadzu Corporation
(column: Tosoh Corporation "TSK-GEL", solvent: tetrahydrofuran
(TMF) and column temperature: 40.degree. C.), it may be determined
from a calibration curve prepared with polystyrene standard
samples.
A commercially available product may be used as the polyester
resin. Examples of the commercially product of the polyester resin
include Elitel KA-5034, Elitel KA-5071S, Elitel KA-1449, Elitel
KA-0134, Elitel KA-3556, Elitel KA-6137, Elitel KZA-6034, Elitel
KT-8803, Elitel KT-8701, Elitel KT-9204, Elitel KT-8904, Elitel
KT-0507, and Elitel KT-9511. These may be used alone or in
combination of two or more kinds. The above-described commercial
products are produced by Unitika Ltd., and "Elitel" is a registered
trademark of the same company.
(2.2.5) Composite Resin
The composite resin that may be contained in the pretreatment
liquid is preferably composite resin particles obtained by
emulsifying a polyolefin resin or a polyacrylic resin in a
polyurethane resin. That is, it is preferable that the composite
resin particles have an inner layer made of a polyolefin resin or a
polyacrylic resin, and a surface layer made of a polyurethane
resin.
Here, the polyurethane resin exists at the interface between the
polyolefin resin or the polyacrylic resin as the water-insoluble
resin and water as the continuous phase, and functions as a
water-insoluble resin particle layer different from the resin for
protecting the water-insoluble resin particles. By using particles
of a composite resin obtained by emulsifying a polyolefin resin or
polyacrylic resin in a polyurethane resin in this way, unlike the
use of the polyolefin resin or polyacrylic resin alone, it is
possible to suppress a decrease in compatibility with the
polyurethane resin or pigment coagulant. In addition, the physical
properties of the image (coating film) may be improved and the
stability of the pretreatment liquid may be improved as compared
with the case where the polyolefin resin or polyacrylic resin and
the polyurethane resin are respectively emulsified and mixed.
In the particles of the composite resin obtained by emulsifying the
polyolefin resin in the polyurethane resin, the value of the mass
ratio (U/O) of the polyurethane resin (U) and the polyolefin resin
(O) is preferably in the range of 40/60 to 95/5. When the presence
ratio of the polyurethane resin (U) is within the above range, the
compatibility with the dispersant is improved, and the solvent
resistance is also improved. Further, when the presence ratio of
the polyolefin resin (O) is in the above range, the adhesion to the
polyolefin film is excellent. In the above-mentioned existence
ratio, the value of the mass ratio (U/O) of the polyurethane resin
(U) and the polyolefin resin (O) is preferably 40/60 to 80/20.
The total resin concentration of the polyolefin resin and the
polyurethane resin in the composite resin particles is not
particularly limited, but is usually 5.0 mass % or more, preferably
in the range of 10.0 to 70.0 mass %. When the resin concentration
is within the above range, the fixing property between the
substrate and the ink becomes good.
In the particles of the composite resin obtained by emulsifying the
polyacrylic resin in the polyurethane resin, the value of the mass
ratio (U/A) of the polyurethane resin (U) and the polyacrylic resin
(A) is preferably in the range of 40/60 to 95/5. When the presence
ratio of the polyurethane resin (U) is within the above range, the
compatibility with the dispersant is improved, and the solvent
resistance is also improved. Further, when the presence ratio of
the polyacrylic resin (A) is in the above range, the adhesion to
the polyolefin film is excellent. In the above-mentioned existence
ratio, the value of the mass ratio (U/A) of the polyurethane resin
(U) and the polyacrylic resin (A) is preferably 40/60 to 80/20.
The total resin concentration of the polyacrylic resin and the
polyurethane resin in the composite resin particles is not
particularly limited, but is usually 5.0 mass % or more, preferably
in the range of 10.0 to 70.0 mass %. When the resin concentration
is within the above range, the fixing property between the
substrate and the ink becomes good.
Further, in the emulsification of the polyolefin resin or the
polyacrylic resin with the polyurethane resin, a surfactant acting
as an emulsifier may be used together with the polyurethane resin.
Here, the storage stability of the particles of the composite resin
may be improved by adding an emulsifier.
An anionic surfactant and a nonionic surfactant may be used as the
emulsifier. In the present invention, it is preferable to use
either one of the anionic surfactant and the nonionic surfactant,
and it is more preferable to use both of them. Here, the total
amount of the anionic surfactant and nonionic surfactant blended is
preferably 1.0 to 20.0 parts by mass with respect to 100 parts by
mass of the total resin. Further, by setting the total amount of
the anionic surfactant and the nonionic surfactant to be 20.0 parts
by mass or less, water resistance and solvent resistance may be
improved.
The value of the blending mass ratio (X/Y) of the anionic
surfactant (X) to the nonionic surfactant (Y) is preferably in the
range of 100/0 to 50/50. By making the blending quantity of an
anionic surfactant in this range, emulsifying ability and storage
stability may be further improved.
Examples of the anionic surfactant that may be used for
emulsification include alkyl sulfate, polyoxyethylene alkyl ether
sulfate, sulfosuccinate, alpha olefin sulfonate, N-acyl amino acid
salt, carboxylate, and phosphoric acid ester. Among these,
sulfosuccinate and alpha olefin sulfonate are favorable. The type
of salt is not particularly limited, but a metal salt such as a
sodium salt, a potassium salt, a magnesium salt, or a
triethanolamine salt, is preferable.
Examples of the nonionic surfactant that may be used for
emulsification include polyoxyethylene alkyl ethers,
polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamine
ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid
esters, and sucrose fatty acid esters. Among these,
polyoxyethylenealkyl ethers and polyoxyethylenealkylphenyl ethers
are preferable.
The average particle diameter of the particles of the composite
resin described above is not particularly limited, but is
preferably 10 to 500 nm, mom preferably 10 to 300 nm, and further
preferably 10 to 200 nm. The average particle diameter may be
measured by a commercially available particle size measuring device
using a dynamic light scattering method or an electrophoretic
method. The measurement by the dynamic light scattering method is
simple, and the particle diameter region may be measured
accurately.
By using particles of a composite resin obtained by emulsifying a
polyolefin resin or a polyacrylic resin in a polyurethane resin,
the fixability of an image (coating film) on a low-absorbent
substrate or a non-absorbent substrate may be improved.
The particles of the composite resin described above may be those
obtained by the methods (I) and (II) for producing particles of a
composite resin using a polyolefin and a polyurethane resin, which
will be described later. It may be one obtained by the method (III)
or (IV) for producing particles of a composite resin using a
polyacrylic resin and a polyurethane resin.
In the pretreatment liquid according to the present invention, an
antioxidant, a light-resistant agent, a plasticizer, a foaming
agent, a thickener, a colorant, a flame retardant, other
water-insoluble resin particles and various fillers may be
added.
Further, various crosslinking agents such as epoxy type,
carbodiimide type, oxazolidine type, blocked isocyanate type, and
isocyanate type may be added to the pretreatment liquid according
to the present invention in order to impart higher durability.
(2.3) Method for Producing Composite Resin Particles
The method for producing the composite resin particles according to
the present invention will be described.
The composite resin particles described above may be prepared by
the following preparation method (I) to (IV).
(2.3.1) Preparation Method (I)
The preparation method (I) is a method in which a polyolefin resin
is emulsified in water with a urethane prepolymer having a
hydrophilic group, and then an amine as a chain extender or an
aqueous solution thereof is added to chain-extend the urethane
prepolymer (to obtain a high molecular weight compound).
In preparation method (I), first, a resin solution obtained by
dissolving a polyolefin resin in a solvent and a solution of a
urethane prepolymer having a hydrophilic group are mixed, and water
is added to the mixture and stirred to emulsify the mixture.
Examples of the solvent include organic solvents such as hexane,
isohexane, pentane, cyclohexane, methylcyclohexane, heptane,
isooctane, methyl ethyl ketone, xylene, toluene and benzene, and
solvents other than water such as carbon dioxide in a supercritical
state. These may be used alone or in combination of two or more
kinds.
The emulsification method may be any known method such as forced
emulsification method, phase inversion emulsification method,
D-phase emulsification method, and gel emulsification method. The
equipment used may be, for example, single stirring with a stirring
blade, a disper, and a homogenizer. It is also possible to use
combined stirring combining these, a sand mill, or a multi-screw
extruder. In addition, the above-mentioned surfactant may be mixed
together with the urethane prepolymer during the
emulsification.
Then, after diluting the above-mentioned emulsion with water, an
amine as a chain extender is added, and the remaining isocyanate
group of the urethane prepolymer is crosslinked by the chain
extender, and the polyurethane resin is polymerized. Thereafter, by
distilling off the organic solvent, a composite resin particle
dispersion (that is, a dispersion in which water-insoluble resin
particles are dispersed) containing a polyolefin resin inside the
polyurethane resin is obtained.
In the composite resin particle dispersion thus obtained, when the
polyolefin resin is a modified polyolefin, the acid component
introduced into the polymer may be neutralized by adding a basic
substance. By ionizing the same portion by neutralization, the
composite resin particle dispersion may further increase the
stability because the polymer molecules am elongated and the entire
system causes a viscosity increase. In this case, the desired pH
may be adjusted by the addition amount of the basic substance.
The basic substance to be used is not particularly limited as long
as it can neutralize the acid moiety in the polyolefin resin.
Examples of the basic substance that may be used in the present
invention include: organic basic substances such as methylamine,
ethylamine, propylamine, butylamine, hexylamine, octylamine,
ethanolamine, propanolamine, dimethylamine, diethylamine,
dipropylamine, dipropylamine, dibutylamine, dihexylamine,
dioctylamine, diethanolamine, dipropanolamine,
N-methyldiethanolamine, triethylamine, N,N-dimethylethanolamine,
2-dimethylamino-2-methyl-1-propanol, 2-amine-2-methyl-1-propanol,
and morpholine; and inorganic basic substance such as an aqueous
ammonia solution, sodium hydroxide, potassium hydroxide, sodium
carbonate, sodium hydrogencarbonate, ammonium carbonate, and
potassium carbonate. When these basic substances am used, the
purpose of the present invention may often be achieved mom
effectively by using two or more types of basic substances in
combination. In addition, when an amine is used as a basic
substance, a tertiary amine is used so that it may not react with
free isocyanate as what is added before making a urethane
prepolymer chain-extend. On the other hand, when neutralizing
modified polyolefin after chain extension, any of primary,
secondary and tertiary amines may be used.
The amount of the basic substance used for neutralization varies
depending on the degree of modification of the modified polyolefin,
and it is preferably in the range of 0.1 to 10.0 parts by mass with
respect to 100.0 parts by mass of the modified polyolefin. When the
amount of the basic substance is 0.1 parts by mass or more, the pH
becomes neutral, and as a result, the storage stability of the
composite resin particle dispersion is improved. On the other hand,
when the amount of the basic substance is 10.0 parts by mass or
less, the storage stability of the composite resin particle
dispersion is good, the basicity is not strong, and a large amount
of hydrophilic substance is not introduced into the image (coating
film). Thereby, water resistance is improved.
(2.3.2) Preparation Method (II)
The preparation method (II) will be described. In the preparation
method (II), a urethane prepolymer having a hydrophilic group is
emulsified in water, and an amine compound as a chain extender or
an aqueous solution thereof is added to extend the chain of the
urethane prepolymer to form an aqueous dispersion of a polyurethane
resin. It is a method of preparing and emulsifying a polyolefin
resin with an aqueous dispersion of a polyurethane resin.
In the preparation method (II), water is added to a solution of a
urethane prepolymer having a hydrophilic group to emulsify. Then,
an amine compound as a chain extender is added to the obtained
emulsion, and the residual isocyanate groups of the urethane
prepolymer am crosslinked with the chain extender to prepare an
aqueous dispersion of a high molecular weight polyurethane
resin.
Thereafter, a resin solution obtained by dissolving a polyolefin
resin in a solvent and the aqueous dispersion of the polyurethane
resin having a hydrophilic group obtained above am mixed. Thereby,
the polyolefin resin is emulsified in the polyurethane resin having
the hydrophilic group. Then, after diluting with water, the organic
solvent is distilled off to obtain a composite resin particle
dispersion (that is, a dispersion in which water-insoluble resin
particles are dispersed) containing a polyolefin resin in the
inside of the polyurethane resin.
In the preparation method (II), the same solvent as in the
preparation method (I) may be selected. Further, also with respect
to the emulsification method, the same method as the preparation
method (I) may be used.
The average particle diameter of the composite resin particles is
not particularly limited, but it is preferably in the range of 10
to 500 nm, more preferably in the range of 10 to 300 nm, and still
more preferably in the range of 10 to 200 nm. The average particle
size may be measured by a commercially available particle size
measuring instrument using a dynamic light scattering method or an
electrophoresis method. Among the above-mentioned measuring
methods, the dynamic light scattering method is preferable because
the measurement is simple and the particle size region may be
measured with high accuracy.
These resins may be copolymers using other monomers.
(2.3.3) Preparation Method (III)
In the preparation method (III), a polyacrylic resin is emulsified
in water with a urethane prepolymer having a hydrophilic group,
then, an amine compound as a chain extender or an aqueous solution
thereof is added, and the urethane prepolymer is subjected to chain
extension (high molecular weight).
In the preparation method (III), first, a resin solution obtained
by dissolving a polyacrylic resin in a solvent is mixed with a
solution of a urethane prepolymer having a hydrophilic group, then
water is added to the mixture, and the mixture is stirred to obtain
an emulsion.
Examples of the solvent include organic solvents such as hexane,
isohexane, pentane, cyclohexane, methylcyclohexane, heptane,
isooctane, methyl ethyl ketone, xylene, toluene and benzene, and
solvents other than water such as carbon dioxide in a supercritical
state. These may be used alone or in combination of two or more
kinds.
The emulsification method may be any known method such as forced
emulsification method, phase inversion emulsification method,
D-phase emulsification method, and gel emulsification method. The
equipment used may be, for example, single stirring with a stirring
blade, a disper, and a homogenizer. It is also possible to use
combined stirring combining these, a sand mill, or a multi-screw
extruder. In addition, the above-mentioned surfactant may be mixed
together with the urethane prepolymer during the
emulsification.
Then, after diluting the above-mentioned emulsion with water, an
amine as a chain extender is added, and the remaining isocyanate
group of the urethane prepolymer is crosslinked by the chain
extender, and the polyurethane resin is polymerized. Thereafter, by
distilling off the organic solvent, a composite resin particle
dispersion (that is, a dispersion in which water-insoluble resin
particles are dispersed) containing a polyolefin resin inside the
polyurethane resin is obtained.
(2.3.4) Preparation Method (IV)
The preparation method (IV) will be described. In the preparation
method (IV), a urethane prepolymer having a hydrophilic group is
emulsified in water, and an amine compound as a chain extender or
an aqueous solution thereof is added to extend the chain of the
urethane prepolymer to obtain an aqueous dispersion of a
polyurethane resin. It is a method of preparing and emulsifying a
polyacrylic resin with an aqueous dispersion of a polyurethane
resin.
In the preparation method (IV), water is added to a solution of a
urethane prepolymer having a hydrophilic group to emulsify. Then an
amine compound as a chain extender is added to the obtained
emulsion, and the residual isocyanate groups of the urethane
prepolymer are crosslinked with the chain extender to prepare an
aqueous dispersion of a high molecular weight polyurethane
resin.
Thereafter, a resin solution obtained by dissolving a polyacrylic
resin in a solvent, and an aqueous dispersion of the polyurethane
resin having the hydrophilic group are mixed. Thereby, a
polyacrylic resin is emulsified with a polyurethane resin having a
hydrophilic group. After diluting with water, and by distilling off
the organic solvent, it is possible to obtain a particle dispersion
of a composite resin (dispersion of water-insoluble resin
particles) containing a polyacrylic resin inside a polyurethane
resin.
In the preparation method (IV), the same solvent as in the
preparation method (III) may be selected. Further, also with
respect to the emulsification method, the same method as the
preparation method (III) may be used.
The average particle diameter of the composite resin particles is
not particularly limited, but it is preferably in the range of 10
to 500 nm, more preferably in the range of 10 to 300 nm, and still
more preferably in the range of 10 to 200 nm. The average particle
size may be measured by a commercially available particle size
measuring instrument using a dynamic light scattering method or an
electrophoresis method. Among the above-mentioned measuring
methods, the dynamic light scattering method is preferable because
the measurement is simple and the particle size region may be
measured with high accuracy.
These resins may be copolymers using other monomers.
The weight average molecular weight of the particles of the
composite resin is preferably in the range of 10,000 to 1,000,000.
When the weight average molecular weight (Mw) of the particles of
the composite resin is 10,000 or more, the cohesive force of the
image formed on the low-absorbent substrate or non-absorbent
substrate (coating film) becomes strong, and the adhesiveness of
the coating film is improved. When the weight average molecular
weight (Mw) is 1,000,000 or less, the solubility with respect to
the organic solvent is good, and particle size reduction of the
emulsified dispersion is accelerated. The weight average molecular
weight (Mw) is a value measured by gel permeation chromatography
(GPC. For example, by using "RID-6A" manufactured by Shimadzu
Corporation (column: Tosoh Corporation "TSK-GEL", solvent:
tetrahydrofuran (THF) and column temperature: 40.degree. C.), it
may be determined from a calibration curve prepared with
polystyrene standard samples.
Although the method for preparing particles of the composite resin
has been described as the water-insoluble resin particles, the
present invention is not limited to this, and a commercially
available composite resin may be used. An example thereof is a
commercially available urethane acrylic resin "WEM-202U" (made by
Taisei Fine Chemical Co., Ltd.).
(2.4) Solvent
The pretreatment liquid may contain an organic solvent as a
solvent. The organic solvent may be selected from the group
consisting of glycols, mono-alcohols and alkanediols described
above. The organic solvents mentioned above may be used alone or in
combination of two or more kinds. The solvent may be removed by the
subsequent pretreatment liquid drying step.
(2.5) Surfactant
The pretreatment liquid may further contain a surfactant. As the
surfactant, in addition to the surfactant represented by Formula
(1), "OLFIN E1010" made by Nissin Chemical Industry Co., Ltd.
("OLFIN" is a registered trademark of the same company), "ECOSURF
EH-6" and "TERGITOL TMN-6" made by Dow Chemical Co., Ltd.,
"BYK-333" made by BYK-Chemie ("BYK" is a registered trademark of
the same company) may be used. By adding a surfactant to the
pretreatment liquid, compatibility with various applying methods
may be enhanced.
(2.6) Water and Other Ingredients
The pretreatment liquid may further contain a cross-linking agent,
a fungicide, and a bactericide as long as the effects of the
present invention are not impaired. The water contained in the
pretreatment liquid is not particularly limited, and may be
ion-exchanged water, distilled water, or pure water.
(3) Substrate
As the substrate according to the present invention, it is
preferable to use a low-absorbent substrate or a non-absorbent
substrate as a recording medium. In the present invention, the
recording medium of the low-absorption substrate or the
non-absorbent substrate is defined based on the measurement result
of the wettability of the surface of the recording medium to water
shown below.
That is, 0.5 .mu.L of water droplet is dropped on the recording
surface of the recording medium, and the decrease rate of the
contact angle (comparison between the contact angle at 0.5
milliseconds after landing and the contact angle at 5 seconds) is
measured. Absorption performance is characterized by this. More
specifically, a recording medium having a non-absorbent substrate
as a property of the recording medium is a recording medium having
a characteristic that the reduction rate of the contact angle is
less than 1.0%. The recording medium having a low absorbent
substrate is a recording medium having the characteristics that the
reduction rate of the contact angle is 1.0% or more and less than
5.0%. Further, the absorbent substrate is defined as a recording
medium having a reduction rate of the contact angle of 5.0% or mom.
The contact angle may be measured using a portable contact angle
meter "PCA-1" (manufactured by Kyowa Interface Science Co.,
Ltd.).
In the present invention, a film may be used as the recording
medium.
Examples of such films include known plastic films. Specific
examples of the plastic film described above include a polyethylene
temphthalate (PET) film, a polyethylene (PE) film, a polypropylene
(PP) film, a nylon (NY) film, a polystyrene (PS) film, an
ethylene-vinyl acetate copolymer (EVA) film, a polyvinyl chloride
(PVC) film, a polyvinyl alcohol (PVA) film, a polyacrylic acid
(PAA) film, a polycarbonate film, a polyacrylonitrile film, and a
biodegradable film such as a polylactic acid film.
In order to impart a gas barrier property, a moisture proof
property, and an odor retention property, the film may be coated
with polyvinylidene chloride on a single surface or on both
surfaces of the film, and the film may be vapor-deposited with
metal oxide. In addition, the film may be subjected to antifogging
treatment. In addition, the film may be subjected to corona
discharge and ozone treatment.
The film may be either an un-stretched film or a stretched film.
The film may also be a multi-layered substrate in which a layer
such as PVA coat is provided on the surface of an absorbent
substrate such as paper to make the area to be recorded
non-absorbent.
(4) Printed Matter
The printed matter of the present invention is provided with a
printing layer containing the inkjet ink contained in the inkjet
recording liquid set and a pretreatment layer containing the
pretreatment liquid.
In the printed matter of the present invention, the pretreatment
liquid is ejected from an inkjet head on a substrate to form a
pretreatment layer, and the inkjet ink is ejected from the inkjet
head to a position where the pretreatment layer is applied and
fixed to form a printing layer.
Further, another functional layer may be formed between the
substrate and the pretreatment layer, and a non-absorbent film
substrate may be attached to the upper layer of the printing layer
via a laminate adhesive layer, for example.
(5) Inkjet Recording Method
The inkjet recording method of the present invention is
characterized in that an image is recorded on a low-absorbent
substrate or a non-absorbent substrate by using the inkjet
recording liquid set. Specifically, the inkjet recording method of
the present invention contains the following steps: a pretreatment
liquid applying step of applying the above-mentioned pretreatment
liquid onto a recording medium (for example, the above-mentioned
film) of a low-absorbent substrate or a non-absorbent substrate; a
pretreatment liquid drying step of forming a pretreatment layer by
drying the pretreatment liquid applied on the low-absorbent
substrate or the non-absorbent substrate; an ink applying step of
applying the above-mentioned inkjet ink by an inkjet method on the
above pretreatment layer, and an ink drying step of forming a
printing layer by drying the ink applied on the pretreatment
layer.
(5.1) Pretreatment Liquid Applying Step
In the step of applying the pretreatment liquid, the
above-mentioned pretreatment liquid is applied onto the recording
medium of the low-absorbent substrate or the non-absorbent
substrate.
The method of applying the pretreatment liquid onto the recording
medium of the low-absorbent substrate or the non-absorbent
substrate is not particularly limited, but preferable examples
thereof include a roller coating method, a curtain coating method,
a spray coating method, and an inkjet method. Among them, the
roller coating method is preferable since it may be used by
connecting a roller coating machine to an inkjet recording
apparatus and may be efficiently applied even when the viscosity is
relatively high.
(5.2) Pretreatment Liquid Drying Step
The pretreatment liquid drying step is a step of forming a
pretreatment layer by drying the pretreatment liquid applied on the
recording medium of the low-absorbent substrate or the
non-absorbent substrate.
The drying of the pretreatment liquid is preferably performed under
the condition that the resin particles contained in the
pretreatment liquid are not completely fused while removing the
solvent components such as water and water-soluble organic solvent.
The drying temperature of the pretreatment liquid is preferably in
the range of 50 to 100.degree. C., for example. The drying time of
the pretreatment liquid is preferably in the range of 3 to 30
seconds, for example.
The pretreatment liquid may be dried, for example, using a
non-contact heating type drying device such as a drying furnace or
a hot air blower, or a contact heating type drying device such as a
hot plate or a heat roller.
The drying temperature may be obtained by measuring any one of the
following during the entire period of drying the pretreatment
liquid: (a) in the case of using a non-contact heating type drying
device such as a drying oven or a hot air blower, an ambient
temperature such as a temperature inside the oven or a hot air
temperature; (b) in the case of using a contact heating type drying
device such as a hot plate or a heat roller, the temperature of the
contact heating part; and (c) the surface temperature of the
surface to be dried. As the measurement location, it is more
preferable to measure (c) the surface temperature of the surface to
be dried.
The thickness of the obtained pretreatment layer is preferably in
the range of 0.3 to 3.0 .mu.m, and more preferably the thickness of
the pretreatment layer is in the range of 0.5 to 2 .mu.m. When the
thickness of the pretreatment layer is 0.3 .mu.m or more, it is
easy to enhance image adhesion and laminate strength while
suppressing ink bleeding. When the thickness of the pretreatment
layer is 3.0 .mu.m or less, the deformation stress due to moisture
or heat may be reduced, so that the adhesiveness of images and the
laminating strength are less likely to be impaired.
(5.3) Ink Application Step
In the ink application step, the inkjet ink of the above-described
inkjet recording liquid set is applied by an inkjet method onto a
recording medium having a low-absorbent substrate or a
non-absorbent substrate.
The inkjet method is not particularly limited, and a printer
including an inkjet head loaded with an ink may be used.
Specifically, an ink may be ejected as droplets from a nozzle of an
inkjet head based on a digital signal, and the droplets may be
landed on a pretreatment layer of a film substrate to perform
printing.
The inkjet head that is used in the inkjet printing method for the
present invention may be an on-demand system or a continuous
system. Further, as a discharge method, any discharge method such
as an electro-mechanical conversion method (for example, single
cavity type, double cavity type, bender type, piston type, shear
mode type, and shared wall type), or an electro-thermal conversion
method (for example, thermal inkjet, and a bubble jet (registered
trademark)) may be used.
Among the above-described inkjet heads, it is preferable to use an
inkjet head (also referred to as a piezo inkjet head) employing a
piezoelectric element as the electro-mechanical conversion element
used in the electro-mechanical conversion system.
Further, the inkjet head may be either a scan type or a line type,
but a line type is preferable.
The line head type inkjet head refers to an inkjet head having a
length equal to or greater than the width of the printing area. As
the line head type inkjet head, one head may be used that is equal
to or more than the width of the printing range, or a plurality of
heads may be combined to be equal to or more than the width of the
printing range.
Further, it is also preferable to arrange a plurality of heads side
by side so that the nozzles of each other am arranged in a
staggered arrangement to increase the resolution of the heads as a
whole.
The conveying speed of the recording medium of a low-absorbent
substrate or a non-absorbent substrate may be set, for example, in
the range of 1 to 120 m/min. The faster the conveying speed, the
faster the image forming speed. According to the present invention,
the occurrence of bleeding is further suppressed even at a very
high linear velocity in the range of 50 to 120 m/min, which is
applicable in the single-pass inkjet image forming method, and an
image having high fixability may be obtained.
By containing the above water-insoluble resin particles in the
pretreatment liquid, it is possible to improve the fixability of
the image (coating film) on the recording medium of the
low-absorbent substrate or the non-absorbent substrate. In
particular, by using the silicone surfactant represented by Formula
(1), it is possible to uniformly and easily spread the ink on a
low-absorbent substrate such as PP or PET or a non-absorbent
substrate. Therefore, it is possible to improve the fixability of
the image (coating film) on the recording medium of the
low-absorbent substrate or the non-absorbent substrate.
(5.4) Ink Drying Step
In the ink drying step, the ink applied on the recording medium of
the low-absorbent substrate or the non-absorbent substrate is
dried.
Drying the ink mainly removes water and water-soluble organic
solvent, which are solvent components of the ink. The drying
temperature of the ink is preferably in the range of 50 to
100.degree. C., for example. The drying time of the ink is
preferably in the range of 3 to 30 seconds, for example.
The ink may be dried by the same method as the above-mentioned
drying of the pretreatment liquid. Also, the drying temperature of
the ink may be measured in the same manner as the drying
temperature in the above-mentioned pretreatment liquid drying
step.
The image forming method of the present invention may be performed
on a film stored in a roll.
(6) Inkjet Image Forming Apparatus
As shown in the FIGURE, the inkjet image forming apparatus 100
according to the present invention is provided with: a head
carriage 120 having an inkjet head that ejects droplets of an
inkjet ink of an inkjet recording liquid set to land on a region on
a low-absorbent substrate or a non-absorbent substrate 110
(hereinafter simply referred to as "substrate"); and a pretreatment
liquid application unit 130 which applies the above-mentioned
pretreatment liquid to the substrate 110. The inkjet image forming
apparatus 100 may further include a dryer 140 for drying the
pretreatment liquid applied to the surface of the substrate.
In the FIGURE, the pretreatment liquid application unit 130 and the
head carriage 120 are arranged in this order from the upstream side
along the transport direction of the substrate 110 (the direction
of the arrow in the drawing). The arrangement order of these is not
limited to this order and may be set arbitrarily.
However, it is preferable that the pretreatment liquid application
unit 130 and the head carriage 120 are arranged in this order.
The head carriage 120 is equipped with, for example, four inkjet
heads 121. Yellow, magenta, cyan, and black inks are ejected from
the nozzles 122 of the respective inkjet heads 121, and the ink
droplets of the inkjet ink are landed on the areas of the substrate
110 to be landed.
The pretreatment liquid application unit 130 may have any
configuration as long as it may apply the pretreatment liquid to an
area wider than the area on the substrate 110 on which the droplets
of the inkjet ink land. For example, the pretreatment liquid
application unit 130 may be configured to include a dispenser 132
that supplies the pretreatment liquid to the coating roller 131,
and a coating roller 131 that coats the supplied pretreatment
liquid in a film shape.
The configuration of the pretreatment liquid application unit 130
is not limited to this, and the pretreatment liquid may be ejected
from the inkjet head 121 and landed on the substrate 110.
The dryer 140 may be a known dryer such as a warm-air dryer that
blows hot air and an irradiator that irradiates infrared rays or
ionizing radiation. The dryer 140 is provided downstream of the
pretreatment liquid application unit 130 and upstream of the head
carriage 120, and dries the pretreatment liquid before the ejection
of ink jet ink droplets.
Although the embodiments of the present invention have been
described and illustrated in detail, the disclosed embodiments are
made for purpose of illustration and example only and not
limitation. The scope of the present invention should be
interpreted by terms of the appended claims.
EXAMPLES
Hereinafter, the present invention will be specifically described
with reference to examples, but the present invention is not
limited thereto. In the following examples, the operations were
performed at room temperature (25.degree. C.) unless otherwise
specified. Further, unless otherwise specified, ".sup.%" and "part"
mean "mass %" and "part by mass", respectively.
(1) Preparation of Inkjet Ink for Inkjet Recording Liquid Set
The inkjet ink of the inkjet recording liquid set was prepared as
follows.
<Organic Solvent>
As the organic solvent, the following A-1 to A-3 were used.
A-1: 1,2-Butandiol (alkanediol)
A-2: Propylene glycol (glycol)
A-3: 1,4-Butandiol (alkanediol)
<Surfactant>
As surfactants, S-1 to S-8 synthesized in Synthetic Examples below,
and S-9 to S-11 commercially available were used.
Synthetic Example of Surfactant S-1
A five-necked flask equipped with a stirrer, a refluxing condenser
tube, a dropping funnel, a thermometer, and a nitrogen-introducing
tube was charged with 450 parts by mass of allylated polyether
(UNIOX PKA-5008 manufactured by Nippon Oil Co., Ltd.) and 0.01
parts by mass of hexachloroplatinic (IV) hexahydrate
H.sub.2PtC.sub.6 6H.sub.2O (manufactured by Tokyo Chemical
Industries, Ltd.) and nitrogen substitution was conducted. The
mixture was heated to 70.degree. C., then 220 parts by mass of
heptamethyltrisiloxane (manufactured by Aldrich Co., Ltd.) was
dropped over 1 hour, and the reaction vessel was allowed to warm to
110.degree. C. for 4 hours. After the reaction, the unreacted
material was distilled off under reduced pressure to obtain a
silicone surfactant S-1 which was the target silicone surfactant.
The obtained silicone surfactant S-1 is a silicone surfactant
corresponding to R=a methyl group, X=an alkylene group having 3
carbon atoms, m=9, n=0 in Formula (1).
Synthetic Example of Surfactant S-2
A silicone surfactant S-2 was obtained in the same manner as in the
synthetic example of the surfactant S-1 except that 1,600 parts by
mass of an allylated polyether (UNISAFE PKA-5015 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). TI obtained silicone surfactant S-2 is a silicone surfactant
corresponding to R=a butyl group, X=an alkylene group having 3
carbon atoms, m=25, n=6 in Formula (1).
Synthetic Example of Surfactant S-3
A silicone surfactant S-3 was obtained in the same manner as in the
synthetic example of the surfactant S-1 except that 200 parts by
mass of an allylated polyether (UNIOX PKA-5001 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). TI obtained silicone surfactant is a silicone surfactant
corresponding to R=a hydrogen atom, X=an alkylene group having 3
carbon atoms, m=3, n=0 in Formula (1).
Synthetic Example of Surfactant S-4
A silicone surfactant S-4 was obtained in the same manner as in the
synthetic example of the surfactant S-1 except that 1,500 parts by
mass of an allylated polyether (UNIOX PKA-5005 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). TI obtained silicone surfactant is a silicone surfactant
corresponding to R=a hydrogen atom, X=an alkylene group having 3
carbon atoms, m=33, n=0 in Formula (1).
Synthetic Example of Surfactant S-5
A silicone surfactant S-5 was obtained in the same manner as in the
synthetic example of the surfactant S-1 except that 2,000 parts by
mass of an allylated polyether (UNIOX PKA-5013 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). TI obtained silicone surfactant is a silicone surfactant
corresponding to R=a hydrogen atom, X=an alkylene group having 3
carbon atoms, m=22, n=16 in Formula (1).
Synthetic Example of Surfactant S-6
A silicone surfactant S-6 was obtained in the same manner as in the
synthesis example of the surfactant S-1 except that 450 parts by
mass of an allylated polyether (UNIOX PKA-5003 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). TI obtained silicone surfactant is a silicone surfactant
corresponding to R=a hydrogen atom, X=an alkylene group having 3
carbon atoms, m=9, n=0 in Formula (1).
Synthetic Example of Surfactant S-7
A silicone surfactant S-7 was obtained in the same manner as in the
synthesis example of the surfactant S-1 except that 750 parts by
mass of an allylated polyether (UNISEFE PKA-5011 manufactured by
Nippon Oil Co., Ltd.) was used instead of 450 parts by mass of an
allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil Co.,
Ltd.). The obtained silicone surfactant is a silicone surfactant
corresponding to R=a hydrogen atom, X=an alkylene group having 3
carbon atoms, m=12, n=3 in Formula (1).
Synthetic Example of Surfactant S-8
A silicone surfactant S-8 was obtained in the same manner as in the
synthesis example of the surfactant S-1 except that 105 parts by
mass of ethylene glycol monoallyl ether (manufactured by Tokyo
Chemical Industry Co., Ltd.) was used instead of 450 parts by mass
of allylated polyether (UNIOX PKA-5008 manufactured by Nippon Oil
Co., Ltd.). The obtained silicone surfactant is a silicone
surfactant corresponding to R=a hydrogen atom, X=an alkylene group
having 3 carbon atoms, m=1, n=0 in Formula (1).
The following commercial products were used as the surfactants S-9
to S-11.
S-9: BYK-333 (manufactured by BYK-Chemie)
S-10: BYK-348 (manufactured by BYK-Chemie)
S-11: SILFACE SAG503A (manufactured by Nisshin Chemical Co.,
Ltd.)
<Preparation of Pigment Dispersion Liquid G-1>
As a self-dispersing pigment dispersion liquid, a self-dispersing
cyan pigment water dispersion liquid "CAB-O-JET 450C pigment
(Pigment Blue 15:3)" made by Cabot Co., solid content 14% was
used.
<Preparation of Pigment Dispersion Liquid G-2>
A pigment dispersion liquid G-2 was prepared by pre-mixing a
mixture of 18 mass % of pigment (Pigment Blue 15:3), 31.5 mass % of
a pigment dispersant (JONCRYL 819 manufactured by BASF Corporation,
an acid value of 75 mg KOH/g, a solid content of 20 mass %), 20
mass % of ethylene glycol, and ion-exchanged water (remaining
amount: a total amount of 100% by mass). Then the mixture was
dispersed using a sand grinder filled with 50 volume % of 0.5 mm
zirconia beads to obtain a pigment dispersion liquid G-2 having a
pigment content of 18 mass %. The average particle diameter of the
pigment particles contained in the pigment dispersion 2 was 110 nm.
The average particle diameter of the particles was measured by
"Zetasizer 1000Hs" made by Malvern Panalytical Ltd.
<Preparation of Aqueous Inkjet Ink I1>
17.00 parts by mass of the pigment dispersion liquid G-1, 10.00
parts by mass of 1,2-butanediol (A-1), 20.00 parts by mass of
propylene glycol (A-2) and 10.00 parts by mass of 1,4-butanediol
(A-3) as organic solvents, 0.05 parts by mass of a surfactant (S-1)
and ion-exchanged water (remaining amount; 42.95 parts by mass)
were added while stirring. The resulting mixture was filtered
through a 1 .mu.m filter to obtain an aqueous inkjet ink I1. There
was no substantial change in composition before and after
filtration.
<Preparation of Aqueous Inkjet Inks I2 and I3>
Aqueous inkjet inks I2 and I3 were prepared in the same manner as
used for the preparation of the aqueous inkjet ink I1 except that
the composition was changed to that indicated in Table I below.
<Preparation of Aqueous Inkjet Ink I4>
17.00 parts by mass of the pigment dispersion liquid G-2, 10.00
parts by mass of 1,2-butanediol (A-1), 20.00 parts by mass of
propylene glycol (A-2), and 10.00 parts by mass of 1,4-butanediol
(A-3) as organic solvents, 1.00 parts by mass of surfactant (S-2)
and ion-exchanged water (remaining amount; 42.00 parts by mass)
were added while stirring. The resulting mixture was filtered
through a 1 .mu.m filter to obtain an aqueous inkjet ink I4. There
was no substantial change in composition before and after
filtration.
<Preparation of Aqueous Inkjet Inks I5 to I13>
Aqueous inkjet inks I5 to I13 were prepared in the same manner as
used for the preparation of the aqueous inkjet ink I4 except that
the composition was changed to that indicated in Table I below.
TABLE-US-00001 TABLE I Aqueous inkjet Unit: Part by mass ink
composition I1 I2 I3 I4 I5 I6 I7 I8 I9 I10 I11 I12 I13 Organic A-1
10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10- .00
10.00 10.00 solvent A-2 20.00 20.00 20.00 20.00 20.00 20.00 20.00
20.00 20.00 20.00 20- .00 20.00 20.00 A-3 10.00 10.00 10.00 10.00
10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.- 00 10.00 Surfactant
S-1 0.05 3.50 1.00 -- -- -- -- -- -- -- -- -- -- S-2 -- -- -- 1.00
-- -- -- -- -- -- -- -- -- S-3 -- -- -- -- 1.00 -- -- -- -- -- --
-- -- S-4 -- -- -- -- -- 1.00 -- -- -- -- -- -- -- S-5 -- -- -- --
-- -- 1.00 -- -- -- -- -- -- S-6 -- -- -- -- -- -- -- 1.00 -- -- --
-- -- S-7 -- -- -- -- -- -- -- -- 1.00 -- -- -- -- S-8 -- -- -- --
-- -- -- -- -- 1.00 -- -- -- S-9 -- -- -- -- -- -- -- -- -- -- 1.00
-- -- S-10 -- -- -- -- -- -- -- -- -- -- -- 1.00 -- S-11 -- -- --
-- -- -- -- -- -- -- -- -- 1.00 Pigment G-1 17.00 17.00 17.00 -- --
-- -- -- -- -- -- -- dispersant G-2 -- -- 17.00 17.00 17.00 17.00
17.00 17.00 17.00 17.00 17.0- 0 17.00 Water 42.95 39.50 42.00 42.00
42.00 42.00 42.00 42.00 42.00 42.00 42.00 42- .00 42.00 Total mass
parts 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00
100.00 100.00 10- 0.00 100.00 100.00 of inkjet ink
(2) Preparation of Pretreatment Liquid for Inkjet Recording Liquid
Set
Next, the pretreatment liquid of the inkjet recording liquid set
was prepared as follows.
<Water-Insoluble Resin Particles>
As the water-insoluble resin particles, the following commercial
products (C-1 to C-3) and the urethane/polyolefin composite resin
(C-4) prepared below were used.
C-1: Elitel KT-0507 (polyester resin, manufactured by Unitika
Corporation)
C-2: WBR-016U (urethane emulsion, manufactured by Taisei Fine
Chemical Co., Ltd.)
C-3: WEM-202U (acrylic urethane emulsion, manufactured by Taisei
Fine Chemical Co., Ltd.)
C-4: Urethane-polyolefin composite resin prepared as follows
(Synthesis of Urethane Prepolymer Solution)
A four-necked flask equipped with a stirrer, a reflux cooling tube,
a thermometer, and a nitrogen-introducing tube was charged with
182.0 parts by mass of polyester polyol, 22.0 parts by mass of
polyethylene glycol (molecular weight 600), 5.6 parts by mass of
trimethylolpropane, 43.8 parts by mass of
N-methyl-N,N-diethanolamine, 204.0 parts by mass of
4,4'-dicyclohexylmethane diisocyanate, and 216.0 parts by mass of
methyl ethyl ketone. Then the reaction was carried out while
maintaining at 75.degree. C. to obtain urethane prepolymer. To this
urethane prepolymer was added with 46.4 parts by mass of dimethyl
sulfuric acid and reacted at 50 to 60.degree. C. for 30 to 60
minutes to obtain a urethane prepolymer solution having an NCO
content of 2.2% and a nonvolatile content of 50%.
(Preparation of Urethane-Polyolefin Composite Resin C-4)
In a four-necked flask equipped with a stirrer, a reflux cooling
tube, a thermometer, and a nitrogen-introducing tube 3.0 parts by
mass of polyolefin resin "AUROREN 150S" (manufactured by Nippon
Paper Industries Co., Ltd., "AUROREN" is a registered trademark of
the same company), 240.0 parts by mass of methylcyclohexane, and
48.0 parts by mass of methyl ethyl ketone were added, and the
temperature was raised to 80.degree. C. and the mixture was heated
and dissolved. After dissolution, the internal temperature was
maintained at 40.degree. C., and 194.0 parts by mass of the
above-mentioned urethane prepolymer solution (nonvolatile content:
about 50%) was added and mixed. To this solution, 58.0 parts by
mass of ion-exchanged water was added, and after emulsification was
performed using a homogenizer, 570.0 parts by mass of ion-exchanged
water was gradually added and diluted. Then an aqueous solution in
which 1.0 part by mass of ethylenediamine and 12.0 parts by mass of
ion-exchanged water were mixed was gradually added and stirred for
1 hour to perform polymerization. This was subjected to desolvation
under a reduced pressure at 50.degree. C. to obtain a
urethane/polyolefin composite resin C-4 having a nonvolatile
content (solid content as particles) of 30.0 mass %.
<Water-solubleResin>
The following D-1 was used as the water-soluble resin.
D-1: "Pluscoat Z-221" (manufactured by Goo Chemical Co., Ltd.,
"Pluscoat" is a registered trademark of the same company)
<Pigment Coagulant>
The following E-1 to E-3 were used as pigment coagulants.
E-1: Cationic polymer "PAS-H-1L" manufactured by Nittobo Medical
Co., Ltd.
E-2: Organic acid (glutaric acid)
E-3: Polyvalent metal salt (calcium chloride)
(Surfactant)
The following F-1 was used as a surfactant.
F-1: BYK-333 (manufactured by BYK-Chemie)
<Preparation of Pretreatment Liquid P1>
The components shown below were sequentially added with stirring,
and then filtered through a 5.0 .mu.m filter to obtain a
pretreatment liquid P1. The composition did not change
substantially before and after filtration.
TABLE-US-00002 Water-insoluble resin particles (C-1): 18.00 parts
by mass Pigment coagulant (E-1): 4.00 parts by mass Surfactant
(F-1): 1.00 part by mass Ion-exchanged water: 77.00 parts by
mass
<Preparation of Pretreatment Liquids P2 to P7>
Pretreatment liquids P2 to P7 were prepared in the same manner as
used for the preparation of the pretreatment liquid P1 except that
the composition was changed to that shown in Table II below.
TABLE-US-00003 TABLE II Unit: Part by mass Pretreatment liquid
composition P1 P2 P3 P4 P5 P6 P7 Resin Water-insoluble C-1 18.00
18.00 -- -- -- 18.00 -- resin particles C-2 -- -- 18.00 -- -- -- --
C-3 -- -- -- 18.00 -- -- -- C-4 -- -- -- -- 18.00 -- -- Water
soluble D-1 -- -- -- -- -- -- 18.00 resin Pigment Cationic E-1 4.00
-- -- -- -- -- -- dispersant polymer Organic acid E-2 -- 4.00 4.00
-- -- -- 4.00 Polyvalent E-3 -- -- -- 4.00 4.00 -- -- metal salt
Surfactant F-1 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Water 77.00 77.00
77.00 77.00 77.00 81.00 77.00 Total mass parts of 100.00 100.00
100.00 100.00 100.00 100.00 100.00 pretreatment liquid
(3) Evaluation
Images 1 to 22 were formed using the prepared inkjet inks I1 to I13
and the prepared pretreatment liquids P1 to P7, and the image
quality, ejection stability, substrate adhesiveness, and hot water
resistance were evaluated for each image.
<Image Formation for Evaluation>
Images 1 to 22 for evaluation were formed by the following
method.
(Formation of Pretreatment Layer)
Pretreatment liquids P1 to P7 were applied onto a non-absorbent
substrate (OPP film, trade name: FOS, manufactured by Futamura
Corporation)) using a bar coater #10, followed by drying at
60.degree. C. for 5 minutes to prepare a recording medium having a
pretreatment layer with a thickness of 3.2 .mu.m.
(Formation of Printing Layer)
The inkjet inks I1 to I13 were set in an inkjet recording apparatus
(manufactured by Konica Minolta, Inc., 360 dpi, discharge rate 14
.mu.L) having an inkjet recording head of a piezo-type inkjet
nozzle. The inkjet recording apparatus was provided with two
independently driven heads arranged so that the nozzles were
staggered with a head module of 720 dpi.times.720 dpi and installed
on a stage conveying machine so that the nozzle rows were
orthogonal in the conveying direction. An inkjet recording
apparatus was configured so that the head module was filled with
inkjet inks I1 to I13 and a solid image was recorded by a
single-pass method on a pretreatment layer formed on a surface of a
substrate conveyed by a stage conveyor. Using the above head,
inkjet ink droplets were ejected so that a solid image of 720
dpi.times.720 dpi with an ink coverage of 11.2 ml/m.sup.2 was
formed.
<Evaluation of Image Quality>
(Evaluation Method)
The images produced by the above method were visually evaluated. In
the evaluation described below, AA, BB, and CC were judged to be
preferable for practical use.
(Evaluation Criteria)
AA: A good image with excellent ink wettability, uniform image
density without unevenness, and no ink dropout.
BB: A practically acceptable image with good ink wettability,
having a portion of non-uniform density but no ink dropout.
CC: An image in which the ink wettability is slightly insufficient
and there is a portion where the ink has dropout, and there is a
slight amount of white spots
DD: An image in which the ink wettability is insufficient, and
there are many areas where the ink has dropout, and white spots are
noticeable.
<Evaluation of Discharge Stability>
(Evaluation Method)
After leaving the recording apparatus used for forming the above
image at 25.degree. C. and 50% RH for 1 hour, 100 sheets of solid
images (100% printing) were successively printed under the
conditions of a printing width of 100 nm.times.100 nm and a
resolution of 720.times.720 dpi. Thereafter, continuous ejection
(driving) was performed under the conditions that the droplet
amount was 3.5 pl, the droplet velocity was 7.0 m/sec, the ejection
frequency was 40 kHz, and the printing rate was 100%, and the
number of head nozzles missing was measured.
(Evaluation Criteria)
Evaluation was performed according to the following criteria. In
the evaluation described below, AA, BB, and CC were judged to be
preferable for practical use.
AA: Without missing nozzle
BB: Nozzle missing of 1 to 3
CC: Nozzle missing of 4 to 6
DD: Nozzle missing of 7 or mom
<Evaluation of Adhesiveness to Substrate>
(Evaluation Method)
The solid image created by the above-mentioned recording method was
cut with a cutter in a 5.times.5 grid pattern at 1 mm intervals,
and a tape peeling test by a cross cut method was performed.
(Evaluation Criteria)
Evaluation was performed according to the following criteria. In
the evaluation described below, AA, BB, and CC were judged to be
preferable for practical use.
AA: No peeling by tape and it is an excellent level
BB: There is peeling of 1 to 3 squares of cuts in a grid pattern,
but it is a good level.
CC: There is peeling of 4 to 6 squares of cuts in a grid pattern,
but it is a practically acceptable level.
DD: There is peeling of 7 or mom squares of cuts in a grid pattern,
it is practically unacceptable level.
<Evaluation of Hot Water Resistance>
(Evaluation Method)
The above images 1 to 22 were stored at 40.degree. C. for 3 days,
and then cut into strips of 10 cm.times.1 cm so that the solid
portion became a cut end surface to obtain test pieces. The test
piece was treated with hot water for 30 minutes, and the state of
the test piece after the process was visually confirmed, and the
hot water resistance of the image by each ink was evaluated by the
following criteria.
(Evaluation Criteria)
Evaluation was performed according to the following criteria. In
the evaluation described below, AA, BB, and CC were judged to be
preferable for practical use.
AA: No peeling of the test piece
BB: Partial peeling of the test piece occurred, but no significant
peeling occurred.
CC: Large peeling of the test piece occurred.
DD: All image portions are peeled off from the test piece film.
TABLE-US-00004 TABLE III Evaluation Base Inkjet ink Pretreatment
Image Ejection material Hot water Image No. No. liquid No. quality
stability adhesiveness resistance Remarks 1 I1 P1 CC BB CC CC
Present Invention 2 I2 P1 CC CC CC BB Present Invention 3 I3 P1 BB
AA CC BB Present Invention 4 I4 P1 BB AA CC AA Present Invention 5
I4 P2 AA AA CC AA Present Invention 6 I5 P2 AA BB CC BB Present
Invention 7 I6 P2 AA BB CC BB Present Invention 8 I7 P3 AA AA BB AA
Present Invention 9 I8 P3 AA BB BB BB Present Invention 10 I9 P3 AA
AA BB AA Present Invention 11 I4 P4 AA AA AA AA Present Invention
12 I5 P4 AA BB AA BB Present Invention 13 I6 P4 AA BB AA BB Present
Invention 14 I7 P5 AA AA AA AA Present Invention 15 I8 P5 AA BB AA
BB Present Invention 16 I9 P5 AA AA AA AA Present Invention 17 I3
P6 DD AA CC AA Comparative Example 18 I3 P7 BB AA DD AA Comparative
Example 19 I10 P3 DD CC CC CC Comparative Example 20 I11 P3 DD CC
CC CC Comparative Example 21 I12 P3 DD CC CC CC Comparative Example
22 I13 P3 DD CC CC CC Comparative Example
As shown in the above-described results, it was found that the
inkjet recording liquid set of the present invention was superior
to the inkjet recording liquid set of the comparative example in
terms of image quality, ejection stability, substrate adhesiveness,
and hot water resistance.
* * * * *